This invention relates to internal combustion engines having intake and exhaust valve timing arranged to provide fresh gas scavenging of the combustion chamber.
In external-ignition two-stroke internal combustion engines and, where appropriate, four-stroke engines, it is a known procedure to supply fresh gas (air in the case of direct fuel injection or a fuel-air mixture in the case of intake injection or carburetor engines) during an overlap of the open times of the intake and exhaust valve to force the exhaust generated in the combustion chamber during the preceding cycle through the open exhaust valve into an exhaust line. A disadvantage of this known procedure is that, with decreasing engine load, the supply of fresh gas transported into the combustion chamber is reduced so that, with declining engine load the exhaust content of the mixture in the combustion chamber, i.e. the residual combustion component, becomes greater, adversely affecting the speed and completeness of combustion as well as the ease of ignition.